DE2240084A1 - REDUCING CROSS-TALKING IN A DOUBLE CUT HEAD - Google Patents

Description

FHN. 5613, Va / RV.

Dfp! .-! Ng. F.-J. COPPER MAN

1'aic.jiinwalt

Anne: e! Tr: N. Y. Philips' GloeilampenfabriekeD

AkfeNo. PHN-5813
Registration dated: August 15, 1972

Reduction of the crosstalk in a double split head.

The invention relates to a double-slit magnetcope: with at least one provided with one or more input windings. Input head and at least one arranged behind this head in the direction of movement of a magnetic recording medium to be guided along the magnetic head and having one or more output windings
provided output head, wherein the output head and the input head to beic; Sides of a central part are attached, which is formed at least by a? 1εν magnetically highly conductive material.

In magnetic drawing units coupled with sixes

rmngssystemen, the magnetic heads for writing and reading inic: nation on a magnetic recording medium like a magnetic tape,
use a disc or a drum, are usually called Dor: ^gap: J :: a _^t:; netköpfο with at least one input element or input header '.: ri

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at least one output element or output head for writing and sending, Immediately subsequent reading out of information on the magnetizable Medium expires / ends. In a common digital recording system, a such a double-gap magnetic head e.g. a number of input heads each with a " Contain input gap for magnetizing the medium according to the excitation circuit of the head in question supplied information. These heads are arranged side by side transversely to the direction of movement of the magnetizable medium in order to write information in a number of mutually parallel tracks. In addition, there is an equal number of output heads arranged next to one another with output columns for reading out those written in the tracks Information available. The input and output heads are in motion direction of the medium arranged one behind the other and the output heads work at the same time πΰΐ the input heads to control the written information and / or to bring information to the outside world.

In the current one with high speeds and high information densities effective recording systems, the respective input and output heads are very close to each other. In this context it is characterizing that the distance between the input and the output gap in a certain type of double gap head is only 3.8 nm, so that the mutual influence is considerable. When registered, ;; Namely, an electro-magnet from the electrical winding of the input head table field is generated which influences the output head and of the output circle is detected. In certain cases such a crosstalk signal even overrule the information signal, resulting in a reliable readout is made impossible.

The above-described problem of crosstalk between Registered and read-out is known and various-

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Techniques proposed to reduce this crosstalk. A significant one Reduction is achieved in that the input and output heads are attached to both sides of a central part that runs through at least one plate of magnetically highly conductive material is formed and forms a conduction path for the leakage flux. (See e.g. the British Patent specification Kr. 1,024,987).

The present invention relates to crosstalk

between writing and reading in a double-gap magnetic head of the type described above Kind of belittle even further. The double gap magnetic head according to the invention is characterized in that the winding configuration of the input head and the winding configuration of the output head attached asymmetrically to the middle part ".

So far it has been common for double-gap magnetic heads that

either the input and output head electrical windings both are only attached to the outer leg (see e.g. the duutsche Patent application 1.424 · 557) »or both only attached to the inner leg are (see e.g. UK patent application 1.024 * 987) »or both above the inner and outer thighs of the head in question are distributed (see e.g. British patent specification 1 »147-944) · That means that until now the electrical windings of the input and output heads are always symmetrical attached to the smock part.

Surprisingly, it has now been found that the crosstalk between writing and reading out can be considerably less than in the above-mentioned configurations of windings, if according to the invention the winding configurationi; of the input head and that of the output head a.t; .yirin: etr5 sch attached to the middle part.

When reducing the TJeLorspi'echens between input head

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and output head, it has proven to be particularly advantageous when after an embodiment of the inventive magnetic head an input winding is mounted on one leg of the input head and an output winding on one leg of the output head.

A maximum reduction in the crosstalk between writing and reading can be achieved, as has been found, if, according to a further embodiment of the magnetic head according to the invention, the output head and the input head are each surrounded by a shield made of magnetically good but electrically poorly conductive material, and the shield extends parallel to the legs of the heads, si; adjoins the magnetically highly conductive plate of the middle part and continues up to the front surface.

The invention is explained in more detail below, for example with reference to the drawing. Show it:

1 shows a known embodiment of a double gap magnetic head, and

Fig. 2 shows a double gap magnetic head according to the invention.

A number of attempts were made ar. that shown in Fig. 1.

known double-gap magnetic head, which has an input kcp: and an output head 2 contains. A magnetic tape (not shown) is to be passed over the head in the direction χ. The input head and the Dispensing heads are both made of ferrite and one on both sides Mounted middle part, which consists of a ferrite plate 3, to their both sides plates 4 and 5 made of magnetically non-conductive ceramic Material lying.

On each leg a or b of the input head 1 is one electrical winding 6 or 7 attached, the number of turns for the

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both windings is the same »The windings can be excited at the same time (in series) or separately for the write process by means of a center tap 8. An electrical winding 9 or 10 is also attached to each leg a ^r or b ^{1 of} the dispensing head, the number of turns also being the same for the two windings. During the readout process, a signal can be taken from each of the windings separately by means of the center tap 11 or from the series connection of the windings. For explanation, it should be mentioned that the thickness of the plate 3 is 0.5 mm, that the parts adjoining the central part of both the input head 1 and the output head 2 have a dimension of 1 mm in the direction of tape travel Central part removed parts ε-although the input head 1 as well as the output head 2 have a dimension in the tape running direction of 3 mm, and that the distance of the input gap 12 from the output gap 13 is 3 »8 µm. The test conditions were:

Frequency of write signal: "5 kHz;

Write current: 10 or 20 mA, (depending on the fact o: one or two windings have been energized),

Rise / fall time: 50 / usec.

The measurement results given in Table I were obtained reference is made to the figure for the winding configuration and it should be noted that the relative crosstalk is always given, i.e. the crosstalk in comparison to the crosstalk that occurs at a head is measured with * the write signal to the input windings connected in series is supplied and in which the output signal is taken from the output windings connected in series. The measurements are for the Corrected the difference in the number of turns.

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TABLE I.

1 10 Registered mail Winding
on
Thigh b Winding
on
Leg a ¹ Read out. • X rel.
Above-
speak fa 20th Winding
on
Leg a X X Winding
on
Leg b ¹ 100 Write-
current
(n / A) 1 20th X X X X X 108 1 20th X X 108 1 20th X X 166 6th 20th X X X 48 1 20th X X X 184 8th 10 X 52 1 10 X X 212 X X 134 X

On the head used for the measurement, the output circle was shielded in the usual way from the input circuit with the help of mu-metal plates. In the present case, it was an H-shaped configuration used by shielding plates, wherein the connecting leg of the H between the input head 1 and the output head 2 is flush with the ■ Plate 3 was located.

A second series of measurements was made on the same as described above Head carried out ι but instead of a mumetal shield a double cylinder 20 made of ferrite according to FIG. 2 is used became.

The measurement results are given in Table II below. ·

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TABLE II

Registered mail 1 Cries
current
(mA) Winding
on
Leg a Winding
on
Thigh b Reading out. Winding
on
Leg a ¹ Winding
on
Leg V rel.
Above-
speak (^ - 2 10 X X X X 100 3 20th X X X 151 4th 20th X X X 42 5 20th X X 98 6th 20th X ν X 9. 7th 20th X X , -56O 8th 20th X X 36 9 10 X X X 196 10 X X X 36

It can be seen from Tables I and II that with respect to Example 1, the crosstalk in Examples 5, 7 and 9 & is lowest.

Fig. 2 shows the parts of a double gap magnetic head roit

a winding configuration according to the invention before being assembled will.

The head consists of a front part I5, two rear yokes 16 and 17 and a shield 20, which is made of ferrite by a. Double cylinder is formed, which also serves as a housing.

The front part I5 consists of two asymmetrical circular parts 21 and 22 made of ferrite, which together with the rear yoke 16 form the magnetic circuit of the input head, of two asymmetrical circular parts 23 ur.a 2J

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made of ferrite, which together with the rear yoke 17 form the magnetic circuit of the output head form, and from a central part through a central plate 25 is formed from ferrite, on both sides of which two plates 26 and 2 " made of non-magnetic ceramic material are attached. All of these are part cemented together firmly, whereby the cementing of the parts 21 ur.d 22 the input gap 28 and by cementing the parts 23 and 24 the output gap 29 is created. On the long sides of the circle parts are also plates made of non-magnetic ceramic construction material 30 » 30 "and 311 31".

The rear yokes 16 and 17 are also made of ferrite. According to the invention, on the inner handle of the rear yoke 16 is a electrical winding 18 and on the outer leg of the rear yoke 17 a electrical winding 19 attached. The ends of the respective windings can be attached to connecting pins 32, 33 or 34t 35.

During assembly, the rear yokes 16 and 17 are cemented in place with the front part 15 and the whole is integrated into the Ferrite housing 20, on which a mounting plate 41 and a band guide link 42 are attached, inserted. The middle part 36 of the cylinder 20 comes to rest on the ferrite plate 25 of the front part, while the side walls 37 and 38 on the ferrite parts 39i 39 'and 40, 4C of the front part come to rest and thus also serve as a shield.

It has now been found that reducing the Crosstalk that with the above-described arrangement of the electrical Windings is achieved greatly from the exact location of the combination de3 Front part with the rear yokes in relation to the shielding? 0 aUhär. £ ir is.

Because before the combination of the front part ri *

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the back yokes is glued in the shield 20, this shield and this combination can be pushed back and forth in relation to one another in the direction of tape travel and the crosstalk is measured at the same time a position can be found in which crosstalk is minimal.

It has been found that the in Table II

relative crosstalk measured under 5, 7 and 9, to a value of 2 could be reduced, which corresponds to an absolute crosstalk signal of 0.1 mV.

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Claims (3)

-10- 'PHN. 5813. PATENT APPLICATION: / Iy double gap magnetic head with at least one with an or 'ii several input windings provided input head and at least one arranged behind this head in the direction of movement of a magnetic recording medium to be guided along the magnetic head and having a or more output coils provided output head, wherein the input head and the output head attached to both sides of a central part are made of at least one plate with good magnetic conductivity is formed, characterized in that the winding configuration of the input head and the winding configuration of the output head is asymmetrical attached to the middle part. 2. Magnetic head according to claim 1, characterized in that an input wrap on one leg of the input head and an output wrap is attached to one leg of the dispensing head. 3. Magnetic head according to claim 1 or 2, characterized in that the output head and the input head each of a shield from nagiietisch good conductive, but electrically poorly conductive material are surrounded, which extends parallel to the legs of the heads, up to the tape contact surface continues and the magnetically highly conductive plate of the middle part. 11/0995